Tomato is one of the most produced crop plants on earth and growing in the fields and greenhouses all over the world. Breeding with known traits of wild species can enhance stress tolerance of cultivated crops. In this study, we investigated responses of the transcriptome as well as primary and secondary metabolites in leaves of a cultivated and a wild tomato to several abiotic stresses such as nitrogen deficiency, chilling or warmer temperatures, elevated light intensities and combinations thereof. The wild species responded different to varied temperature conditions compared to the cultivated tomato. Nitrogen deficiency caused the strongest responses and induced in particular the secondary metabolism in both species but to much higher extent in the cultivated tomato. Our study supports the potential of a targeted induction of valuable secondary metabolites in green residues of horticultural production, that will otherwise only be composted after fruit harvest. In particular, the cultivated tomato showed a strong induction in the group of mono caffeoylquinic acids in response to nitrogen deficiency. In addition, the observed differences in stress responses between cultivated and wild tomato can lead to new breeding targets for better stress tolerance.

Root temperature has long been considered an essential environmental factor influencing the plant’s physiology. However, little is known about the effect of root temperature on the quality of the food produced by the plant, especially that of horticultural crops. To fill this gap, two independent root cooling experiments (15 °C vs. 20 °C and 10 °C vs. 20 °C) were conducted in autumn 2017 and spring 2018 in hydroponics with Chinese broccoli (Brassica oleracea var. alboglabra Bailey) under greenhouse conditions. The aim was to investigate the effect of root temperature on plant growth (biomass, height, yield) and food quality (soluble sugars, total chlorophyll, starch, minerals, glucosinolates). A negative impact on shoot growth parameters (yield, shoot biomass) was detected by lowering the root temperature to 10 °C. Chinese broccoli showed no response to 15 °C root temperature, except for an increase in root biomass. Low root temperature was in general associated with a higher concentration of soluble sugars and total chlorophyll, but lower mineral levels in stems and leaves. Ten individual glucosinolates were identified in the stems and leaves, including six aliphatic and four indolic glucosinolates. Increased levels of neoglucobrassicin in leaves tracked root cooling more closely in both experiments. Reduction of root temperature by cooling could be a potential method to improve certain quality characters of Chinese broccoli, including sugar and glucosinolate levels, although at the expense of shoot biomass.

The seed pericarp of Chenopodium quinoa Willd. (quinoa) contains a mixture of triterpenoid saponins conferring undesired organoleptic properties. In this study, we evaluated saponin content and their corresponding sapogenins in 114 different quinoa accessions. Relative saponin content ranged from 0.22 to 15.04 mg/g of seed dry weight among the genotypes studied and the genotype effect was significant (p < 0.001). About 75% of the genotypes could be classified as low-saponin content lines which is promising in view of ongoing plant breeding efforts. In addition to the quantitative determination of saponins, metabolic profiling was performed by LC-FTICR-MS and LC-MS/MS. We obtained highly accurate mass estimation from ion spectra allowing the identification of twelve saponins of the oleanane type. These differ in their aglycons and in the number and type of glycoside units. Interestingly, we identified a saponin compound that, to our knowledge, had not been reported previously. Our study highlights that there is considerable variability concerning saponin content in quinoa, which contributes to the valorization of genetic resources towards the identification of genotypes that could be utilized in current and future quinoa breeding programs.